Add a funny sysctl: debug.kdb.trap_code .

It is similar to debug.kdb.trap, except for it tries to cause a page fault
via a call to an invalid pointer.  This can highlight differences between
a fault on data access vs. a fault on code call some CPUs might have.

This appeared as a test for a work \
Sponsored by: RiNet (Cronyx Plus LLC)

1 files changed, 22 insertions, 1 deletions

diff --git a/sys/kern/subr_kdb.c b/sys/kern/subr_kdb.c
index 6b2be99..4b2991c 100644
--- a/sys/kern/subr_kdb.c
+++ b/sys/kern/subr_kdb.c
@@ -62,6 +62,7 @@ static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
 static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
 static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS);
 static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS);
+static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS);
 
 SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes");
 
@@ -78,7 +79,10 @@ SYSCTL_PROC(_debug_kdb, OID_AUTO, panic, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
     kdb_sysctl_panic, "I", "set to panic the kernel");
 
 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
-    kdb_sysctl_trap, "I", "set cause a page fault");
+    kdb_sysctl_trap, "I", "set to cause a page fault via data access");
+
+SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
+    kdb_sysctl_trap_code, "I", "set to cause a page fault via code access");
 
 /*
  * Flag indicating whether or not to IPI the other CPUs to stop them on
@@ -195,6 +199,23 @@ kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
 	return (*addr);
 }
 
+static int
+kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
+{
+	int error, i;
+	void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;
+
+	error = sysctl_wire_old_buffer(req, sizeof(int));
+	if (error == 0) {
+		i = 0;
+		error = sysctl_handle_int(oidp, &i, 0, req);
+	}
+	if (error != 0 || req->newptr == NULL)
+		return (error);
+	(*fp)(0x11111111, 0x22222222, 0x33333333);
+	return (0);
+}
+
 /*
  * Solaris implements a new BREAK which is initiated by a character sequence
  * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the